Acadia National Park - FLOW: Marine Waters Gulf of Maine

O n average, Maine"s rivers pour about 250 billion gallons of fresh water into the Gulf of Maine every year. Add to that astounding volume sediments and nutrients from terrestrial runoff, whirl it into the Gulf"s semi-enclosed basin, and you have a rich recipe for life. The crescent of underwater banks and mountains stretching from Cape Cod to Nova Scotia allows very little exchange between the waters of the Gulf and the Atlantic Ocean. As a result, Maine"s coastal waters tend to be cooler, richer in sediments and nutrients, and more diluted by fresh water than the water beyond Georges and Brown banks.

The main entry into the Gulf of Maine is through the Northeast Channel, a deep underwater valley between Georges and Brown banks. Cold water from the North Atlantic enters the gulf by this means, then circulates counter-clockwise, requiring some three months to make one round of the gulf.

The gulf"s resources are rich, but not inexhaustable. Phytoplankton (microscopic marine plants) supporting the food web depend on nutrients exported by watersheds mixing in the presence of sunlight with nutrients welling up from the deep. Those nutrients are available in limited supply, supporting limited populations of phytoplankton, in turn supporting limited populations of zooplankton (microscopic water-borne animals), invertebrates, sea mammals, and fish. Treating the Gulf as if it were an infinite source, we have mined it beyond its fisheries" capacity to regenerate. The only solution is for humans to back off for a time, and rethink the amount of fish they can take from the gulf. In one year, some 20,000 fishermen typically land some 530,000 metric tons (a metric ton is 2,205 pounds) of fifty-two different species of fish (including both finfish and shellfish) from the Gulf of Maine. In 1993, Canada reported the crash of groundfisheries along its Atlantic coast. Continued declines seemed certain. In 1992, Newfoundland declared a total fishing moratorium.

There are two possible outcomes: either we ask the Gulf of Maine to feed fewer mouths at a sustainable rate, or its fisheries will collapse and be able to feed none at all.

The greatest concentrations of life in the gulf occur in the summer during times when phytoplankton thrive, notably over Georges Bank where the water can be less than 9 feet deep in places. Such areas are among the most biologically productive regions anywhere on Earth.

Who lives in the Gulf of Maine? Bottom-dwelling species including corals, sponges, worms, and many others. Cod, haddock, and pollock are bottom dwelling fish species that feed on creatures on the gulf floor. Several species migrate into the gulf from the North Atlantic, including yellowfin and bluefin tuna, swordfish, dogfish, sharks, menhaden, squids, and great schools of herring. Species that mature in salt water but move into freshwater streams to reproduce include Atlantic salmon, Atlantic sturgeon, alewives, and striped bass.

A variety of marine mammals feed in the gulf during the summer months, including whales, dolphins and porpoises. The most common whales are humpback and finback whales, both baleen whales that gulp plankton by the mouthful. Smaller marine mammals include common dolphins, white-sided dolphins, and harbor porpoises. Harbor seals live in the gulf year-round, and the occasional hooded seal from more arctic waters explores its reaches.

A great many birds feed on fish in the surface waters of the Gulf of Maine, including several species of birds seldom seen on the mainland. Petrels, storm-petrels, shearwaters, northern gannets, auks, and puffins are a few of the birds that fish the Gulf of Maine. There are also the more familiar shoreside birds such as ducks, geese, gulls, terns, herons, cormorants, sandpipers, hawks, and many others.

The southern extent of the Gulf of Maine--from Cape Cod, Massachusetts, to Cape Elizabeth near Portland, Maine, is famous for its sandy beaches. The central region features the familiar rockbound coast where cobble beaches replace the sandy ones. In the northern reaches of the gulf, the Bay of Fundy funnels the tide into ever-narrowing bays that host the highest tides on Earth.